Fuel injection device

ABSTRACT

In an injection hole set, primary and secondary injection holes are formed to satisfy the following relationship: γ≤θt1+θt2−0.87×P{circumflex over ( )}0.52, where γ (deg) is an injection-hole-to-injection-hole angle, which is an angle formed between a primary central axis of the primary injection hole and a secondary central axis of the secondary injection hole; θt1 (deg) is a primary taper angle, which is an angle formed between outlines of a primary injection hole inner wall of the primary injection hole in a cross section of the primary injection hole inner wall; θt2 (deg) is a secondary taper angle, which is an angle formed between outlines of a secondary injection hole inner wall of the secondary injection hole in a cross section of the secondary injection hole inner wall; and P (MPa) is an average pressure of the fuel in a fuel passage at a time of injecting the fuel from the injection holes.

CROSS REFERENCE TO RELATED APPLICATION

This application is the U.S. national phase of International ApplicationNo. PCT/JP2017/002841 filed Jan. 27, 2017, which designated the U.S. andclaims priority to Japanese Patent Application No. 2016-33050 filed onFeb. 24, 2016, the entire contents of each of which are herebyincorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a fuel injection device that injectsfuel.

BACKGROUND ART

Previously, there is known a fuel injection device that includes aplurality of injection holes. The patent literature 1 discloses astructure, in which a diverging angle between a primary injection holeand a secondary injection hole, i.e., aninjection-hole-to-injection-hole angle, which is an angle definedbetween central axes of the injection holes, is set to 15 to 25 degrees.With this setting, the Coanda effect is generated between fuel mistsinjected from the injection holes, so that the fuel mists are pulledtoward each other. In this way, a rich mixture gas, which is atomized,is generated at a center side between the fuel mists.

It is assumed that an inner wall of each injection hole is shaped into acylindrical form, i.e., a straight form at the fuel injection device ofthe patent literature 1. In the case where the inner wall of eachinjection hole is in the straight form, a large difference is generatedbetween: a mist angle, which is an angle defined between outlines of thefuel mist injected from the injection hole at a time of generating ahigh fuel pressure in the fuel injection device; and a mist angle, whichis an angle defined between outlines of the fuel mist injected from theinjection hole at a time of generating a low fuel pressure in the fuelinjection device. Therefore, a degree of the Coanda effect, which isgenerated between the fuel mists injected from the injection holes, maypossibly be changed depending on the fuel pressure in the fuel injectiondevice.

In the fuel injection device of the patent literature 1, in a case wherethe mist angle of the fuel mist injected from each injection hole isexcessively increased at the time of, for example, the high fuelpressure, the Coanda effect may be excessively exerted, so that the fuelmists collide with each other to interfere the atomization of the fuelmist at the center side between the fuel mists. In contrast, in a casewhere the mist angle of the fuel mist injected from each injection holeis excessively reduced at the time of, for example, the low fuelpressure, the Coanda effect may not be exerted, so that theconcentration of the mixture gas at the center side between the fuelmists may possibly be decreased.

CITATION LIST Patent Literature

PATENT LITERATURE 1: JP4085944B2 (corresponding to EP1517017A1)

SUMMARY OF INVENTION

The present disclosure is made in view of the above disadvantage, and itis an objective of the present disclosure to provide a fuel injectiondevice that can stably generate the Coanda effect between two fuel mistsregardless of a change in a fuel pressure.

A fuel injection device of the present disclosure includes a nozzle.

The nozzle includes: a nozzle tubular portion that forms a fuel passagein an inside of the nozzle tubular portion; a nozzle bottom portion thatcloses one end of the nozzle tubular portion; and a plurality ofinjection holes that connect between one surface of the nozzle bottomportion, which is located on a side where the nozzle tubular portion isplaced, and an opposite surface of the nozzle bottom portion, which islocated on an opposite side that is opposite from the nozzle tubularportion, to inject fuel of the fuel passage.

The plurality of injection holes includes at least one injection holeset that includes a primary injection hole and a secondary injectionhole.

The primary injection hole has: a primary inlet opening, which is formedat the one surface of the nozzle bottom portion located on the sidewhere the nozzle tubular portion is placed; a primary outlet opening,which is formed at the opposite surface of the nozzle bottom portionlocated on the opposite side that is opposite from the nozzle tubularportion; and a primary injection hole inner wall, which connects betweenthe primary inlet opening and the primary outlet opening and is taperedsuch that the primary injection hole inner wall is progressively spacedaway from a primary central axis, which is a central axis of the primaryinjection hole, from the primary inlet opening side toward the primaryoutlet opening side.

The secondary injection hole has: a secondary inlet opening, which isformed at the one surface of the nozzle bottom portion located on theside where the nozzle tubular portion is placed; a secondary outletopening, which is formed at the opposite surface of the nozzle bottomportion located on the opposite side that is opposite from the nozzletubular portion; and a secondary injection hole inner wall, whichconnects between the secondary inlet opening and the secondary outletopening and is tapered such that the secondary injection hole inner wallis progressively spaced away from a secondary central axis, which is acentral axis of the secondary injection hole, from the secondary inletopening side toward the secondary outlet opening side.

According to the present disclosure, with respect to the injection holeset, γ (deg) is defined as an injection-hole-to-injection-hole angle,which is an angle formed between the primary central axis and thesecondary central axis; θt1 (deg) is defined as a primary taper angle,which is an angle formed between outlines of the primary injection holeinner wall in a cross section of the primary injection hole inner walltaken along an imaginary plane that includes all of the primary centralaxis; θt2 (deg) is defined as a secondary taper angle, which is an angleformed between outlines of the secondary injection hole inner wall in across section of the secondary injection hole inner wall taken along animaginary plane that includes all of the secondary central axis; and P(MPa) is defined as an average pressure of the fuel in the fuel passageat a time of injecting the fuel from the plurality of injection holes;and the primary injection hole and the secondary injection hole areformed to satisfy a relationship of the following equation 1:γ≤θt1+θt2−0.87×P{circumflex over ( )}0.52  Equation 1Here, {circumflex over ( )} of the equation 1 denotes “to a power of.”

In the present disclosure, the primary injection hole and the secondaryinjection hole are formed to satisfy the equation 1, so that the Coandaeffect can be effectively generated between the fuel mist, which isinjected from the primary injection hole, and the fuel mist, which isinjected from the secondary injection hole.

Furthermore, according to the present disclosure, the primary injectionhole inner wall and the secondary injection hole inner wall are tapered,so that the primary injection hole or the secondary injection holedischarges the fuel to spread the fuel. Therefore, it is possible toreduce a difference between: a mist angle of the fuel mist, which isinjected from each injection hole in the state where the fuel pressurein the fuel passage is high; and a mist angle of the fuel mist, which isinjected from each injection hole in the state where the fuel pressurein the fuel passage is low. Therefore, even when the fuel pressure inthe fuel passage changes, it is possible to limit a change in the mistangle of the fuel mist, which is injected from the primary injectionhole or the secondary injection hole. Thereby, regardless of the changein the fuel pressure, the Coanda effect can be stably generated betweenthe fuel mist, which is injected from the primary injection hole, andthe fuel mist, which is injected from the secondary injection hole.Thus, regardless of the change in the fuel pressure, a rich mixture gas,which is atomized at the center side between the fuel mists, can bestably generated.

BRIEF DESCRIPTION OF DRAWINGS

The present disclosure, together with additional objectives, featuresand advantages thereof, will be best understood from the followingdescription in view of the accompanying drawings.

FIG. 1 is a cross-sectional view showing a fuel injection deviceaccording to a first embodiment of the present disclosure.

FIG. 2 is a diagram showing a state where the fuel injection deviceaccording to the first embodiment of the present disclosure is appliedto an internal combustion engine.

FIG. 3 is a cross-sectional view showing injection holes and itsadjacent area of the fuel injection device according to the firstembodiment of the present disclosure.

FIG. 4 is a view taken in a direction of an arrow IV in FIG. 3.

FIG. 5 is a schematic diagram showing a relationship among the injectionholes of the fuel injection device according to the first embodiment ofthe present disclosure.

FIG. 6 is a schematic diagram showing a positional relationship amongfuel mists injected from the fuel injection device according to thefirst embodiment of the present disclosure.

FIG. 7 is a diagram indicating a relationship between γ−(θt1+θt2) and adegree of influence of the Coanda effect.

FIG. 8 is a schematic diagram showing a positional relationship amongfuel mists injected from a fuel injection device according to a secondembodiment of the present disclosure.

FIG. 9 is a schematic diagram showing a relationship among injectionholes of a fuel injection device according to a third embodiment of thepresent disclosure.

FIG. 10 is a diagram showing a state where a fuel injection deviceaccording to a fourth embodiment of the present disclosure is applied tothe internal combustion engine.

FIG. 11 is a schematic diagram showing a positional relationship amongfuel mists injected from the fuel injection device according to thefourth embodiment of the present disclosure.

FIG. 12 is a schematic diagram showing a positional relationship amongfuel mists injected from a fuel injection device according to a fifthembodiment of the present disclosure.

FIG. 13 is a schematic diagram showing a positional relationship amongfuel mists injected from a fuel injection device according to a sixthembodiment of the present disclosure.

DESCRIPTION OF EMBODIMENTS

Hereinafter, various embodiments of the present disclosure will bedescribed with reference to the drawings. In the following embodiments,substantially identical structural portions will be indicated by thesame reference signs and will not be described redundantly for the sakeof simplicity.

First Embodiment

FIG. 1 indicates a fuel injection device according to a first embodimentof the present disclosure. The fuel injection device 1 is applied to,for example, a gasoline engine (hereinafter simply referred to as anengine) 80, which serves as an internal combustion engine, to injectgasoline, which serves as fuel, in the engine 80 (see FIG. 2).

As shown in FIG. 2, the engine 80 includes: a cylinder block 81, whichis shaped into a cylindrical tubular form; a piston 82; a cylinder head90; an intake valve 95; and an exhaust valve 96. The piston 82 isoperable to reciprocate in an inside of the cylinder block 81. Thecylinder head 90 is installed such that the cylinder head 90 closes anopening end of the cylinder block 81. A combustion chamber 83 is definedby an inner wall of the cylinder block 81, a wall surface of thecylinder head 90 and the piston 82. A volume of the combustion chamber83 is increased and then decreased in response to reciprocation of thepiston 82.

The cylinder head 90 includes an intake manifold 91 and an exhaustmanifold 93. An air intake passage 92 is formed in the intake manifold91. One end of the air intake passage 92 is opened to the atmosphere,and the other end of the air intake passage 92 is connected to thecombustion chamber 83. The air intake passage 92 conducts the air(hereinafter referred to as intake air), which is suctioned from theatmosphere, to the combustion chamber 83.

An exhaust passage 94 is formed in the exhaust manifold 93. One end ofthe exhaust passage 94 is connected to the combustion chamber 83, andthe other end of the exhaust passage 94 is opened to the atmosphere. Theexhaust passage 94 conducts the air (hereinafter referred to as exhaustgas), which includes combustion gas generated in the combustion chamber83, to the atmosphere.

The intake valve 95 is installed to the cylinder head 90 such that theintake valve 95 is operable to reciprocate through rotation of a cam ofa driven-side shaft that is rotated synchronously with rotation of adrive shaft (not shown). The intake valve 95 is operable to open andclose a connection between the combustion chamber 83 and the air intakepassage 92 through reciprocation of the intake valve 95. The exhaustvalve 96 is installed to the cylinder head 90 such that the exhaustvalve 96 is operable to reciprocate through rotation of a cam. Theexhaust valve 96 is operable to open and close a connection between thecombustion chamber 83 and the exhaust passage 94 through reciprocationof the exhaust valve 96.

In the present embodiment, the fuel injection device 1 is installed to aside of the air intake passage 92 of the intake manifold 91, at whichthe cylinder block 81 is placed. The fuel injection device 1 is placedsuch that an axis of the fuel injection device 1 is tilted relative toan axis of the combustion chamber 83 or is skew to the axis of thecombustion chamber 83. In the present embodiment, the fuel injectiondevice 1 is placed on a lateral side of the combustion chamber 83. Thatis, the fuel injection device 1 is mounted to the lateral side of theengine 80.

Furthermore, a spark plug 97, which serves as an ignition device, isplaced at a corresponding location of the cylinder head 90, which isbetween the intake valve 95 and the exhaust valve 96, i.e., acorresponding location of the cylinder head 90 that corresponds to acenter of the combustion chamber 83. The spark plug 97 is placed at thelocation where the fuel injected from the fuel injection device 1 doesnot directly adhere to the spark plug 97, and the spark plug 97 canignite the mixture gas (combustible air), which is a mixture of the fueland the intake air. As discussed above, the engine 80 is a directioninjection gasoline engine.

The fuel injection device 1 is placed such that a plurality of injectionholes 13 of the fuel injection device 1 is exposed to a radially outerportion of the combustion chamber 83. Pressurized fuel, which ispressurized to a pressure corresponding to a fuel injection pressure bya fuel pump (not shown), is supplied to the fuel injection device 1. Aconical fuel mist Fo is injected from the respective injection holes 13of the fuel injection device 1 into the combustion chamber 83. When thefuel mist Fo is injected from the respective injection holes 13, anegative pressure Vc is generated between each adjacent two of the fuelmists Fo. Thereby, each adjacent fuel mists Fo are pulled toward eachother. This phenomenon is known as the Coanda effect.

Next, a basic structure of the fuel injection device 1 will be describedwith reference to FIG. 1.

The fuel injection device 1 includes a nozzle 10, a housing 20, a needle30, a movable core 40, a stationary core 41, a spring 43 (serving as avalve seat side urging member) and a coil 44.

The nozzle 10 is made of metal, such as martensitic stainless steel. Thenozzle 10 is processed through a quenching process, so that the nozzle10 has a predetermined degree of hardness. As shown in FIG. 1, thenozzle 10 includes a nozzle tubular portion 11, a nozzle bottom portion12, the injection holes 13 and a valve seat 14.

The nozzle tubular portion 11 is shaped into a tubular form. The nozzlebottom portion 12 closes one end of the nozzle tubular portion 11. Eachof the injection holes 13 is configured to connect between one surface121, i.e., an inner wall of the nozzle bottom portion 12, which islocated on a side where the nozzle tubular portion 11 is placed, and anopposite surface 122, i.e., an outer wall of the nozzle bottom portion12, which is located on an opposite side that is opposite from thenozzle tubular portion 11 (see FIG. 3). The injection holes 13 areformed as a plurality of injection holes at the nozzle bottom portion12. In the present embodiment, the number of the injection holes 13 issix (see FIG. 4). The valve seat 14 is formed in a form of a ring aroundthe injection holes 13 on a side of the nozzle bottom portion 12 wherethe nozzle tubular portion 11 is placed. The injection holes 13 will bedescribed in detail later.

The housing 20 includes a nozzle holder 26, a first tubular member 21, asecond tubular member 22, a third tubular member 23, an inlet portion 24and a filter 25.

The nozzle holder 26 is shaped into a tubular form and is made of amagnetic material, such as ferritic stainless steel. An opposite endpart of the nozzle tubular portion 11, which is opposite from the nozzlebottom portion 12, is connected to an inner side of one end of thenozzle holder 26. The nozzle holder 26 and the nozzle 10 are joinedtogether by, for example, welding. In this way, the nozzle holder 26holds the nozzle 10.

The first tubular member 21, the second tubular member 22 and the thirdtubular member 23 are respectively shaped into a generally cylindricaltubular form. The first tubular member 21, the second tubular member 22and the third tubular member 23 are coaxially arranged one after anotherin this order and are joined together.

The first tubular member 21 and the third tubular member 23 are made ofa magnetic material, such as ferritic stainless steel, and are processedthrough a magnetically-stabilizing process. The first tubular member 21and the third tubular member 23 have a relatively low degree ofhardness. In contrast, the second tubular member 22 is made of anon-magnetic material, such as austenitic stainless steel. A degree ofhardness of the second tubular member 22 is higher than the degree ofhardness of the first tubular member 21 and the third tubular member 23.

An outer wall of an opposite end part of the first tubular member 21,which is opposite from the second tubular member 22, is fitted to aninner wall of an opposite end part of the nozzle holder 26, which isopposite from the nozzle 10.

The inlet portion 24 is shaped into a tubular form and is made of amagnetic material, such as ferritic stainless steel. One end of theinlet portion 24 is joined to an opposite end part of the third tubularmember 23, which is opposite from the second tubular member 22.

A fuel passage 100 is formed in an inside of the housing 20. The fuelpassage 100 is connected to the injection holes 13. Specifically, thenozzle tubular portion 11 forms the fuel passage 100 in an inside of thenozzle tubular portion 11. A pipe (not shown) is joined to an oppositeside of the inlet portion 24, which is opposite from the third tubularmember 23. Thereby, fuel, which is fed from a fuel supply source (fuelpump), is supplied to the fuel passage 100 through the pipe. The fuelpassage 100 conducts the fuel to the injection holes 13.

The filter 25 is installed in an inside of the inlet portion 24. Thefilter 25 collects foreign objects, which are contained in the fuelsupplied to the fuel passage 100.

The needle 30 is shaped into a rod form and is made of metal, such asmartensitic stainless steel. The needle 30 is processed through aquenching process, so that the needle 30 has a predetermined degree ofhardness. The degree of hardness of the needle 30 is set to besubstantially the same as the degree of hardness of the nozzle 10.

The needle 30 is received in the inside of the housing 20 such that theneedle 30 is operable to reciprocate in the fuel passage 100 in theaxial direction of the housing 20. The needle 30 has a seat portion 31and a large diameter portion 32.

The seat portion 31 is formed at an end part of the needle 30 located onthe nozzle 10 side and is contactable with the valve seat 14.

The large diameter portion 32 is formed near the seat portion 31 at theend part of the needle 30 located on the valve seat 14 side. An outerdiameter of the large diameter portion 32 is set to be larger than anouter diameter of the end part of the needle 30 located on the valveseat 14 side. An outer wall of the large diameter portion 32 isconfigured to slide relative to an inner wall of the nozzle tubularportion 11 of the nozzle 10. In this way, the axial reciprocation of theend part of the needle 30, which is located on the valve seat 14 side,is guided. The large diameter portion 32 includes cutouts 33 that areformed by cutting a plurality of circumferential parts of the outer wallof the large diameter portion 32. In this way, the fuel can flow throughgaps, each of which is defined between a corresponding one of thecutouts 33 and the inner wall of the nozzle tubular portion 11.

The needle 30 opens or closes the injection holes 13 when the seatportion 31 of the needle 30 is moved away from (lifted from) the valveseat 14 or contacts (seated against) the valve seat 14. Hereinafter, adirection of moving the needle 30 away from the valve seat 14 will bereferred to as a valve opening direction, and a direction of contactingthe needle 30 to the valve seat 14 will be referred to as a valveclosing direction.

The movable core 40 is shaped into a tubular form and is made of amagnetic material, such as ferritic stainless steel. The movable core 40is processed through a magnetically-stabilizing process. A degree ofhardness of the movable core 40 is relatively low and is substantiallythe same as the degree of hardness of the first tubular member 21 andthe third tubular member 23 of the housing 20.

The movable core 40 includes a first tubular portion 401 and a secondtubular portion 402. The first tubular portion 401 and the secondtubular portion 402 are integrally formed in one piece such that thefirst tubular portion 401 and the second tubular portion 402 are coaxialwith each other. The first tubular portion 401 is formed such that aninner wall of one end of the first tubular portion 401 is fitted to anouter wall of a opposite end part of the needle 30, which is oppositefrom the valve seat 14. In the present embodiment, the movable core 40and the needle 30 are joined together by welding. Therefore, the movablecore 40 is operable to reciprocate together with the needle 30 in theaxial direction in the inside of the housing 20.

The second tubular portion 402 is joined to the other end of the firsttubular portion 401. An outer diameter of the second tubular portion 402is set to be larger than an outer diameter of the first tubular portion401.

Radial holes 403 are formed at the first tubular portion 401 such thateach of the radial holes 403 extends in a radial direction to connectbetween an inner wall and an outer wall of the first tubular portion401. In this way, the fuel can flow between the inside and the outsideof the first tubular portion 401 (the movable core 40) through theradial holes 403.

The movable core 40 includes a projection 404 that radially outwardlyprojects in a form of a ring from an outer wall of an opposite end partof the second tubular portion 402, which is opposite from the firsttubular portion 401. An outer wall of the projection 404 is slidablerelative to the inner wall of the second tubular member 22 of thehousing 20. Therefore, the axial reciprocation of the movable core 40 isguided by the inner wall of the second tubular member 22. Specifically,the axial reciprocation of the needle 30 and the axial reciprocation ofthe movable core 40 in the fuel passage 100 are guided by the inner wallof the nozzle tubular portion 11 and the inner wall of the secondtubular member 22. Furthermore, the movable core 40 includes a steppedsurface 405, which is shaped into a planar ring form and is placed atthe inside of the second tubular portion 402.

The stationary core 41 is shaped into a generally cylindrical tubularform and is made of a magnetic material, such as ferritic stainlesssteel. The stationary core 41 is processed through amagnetically-stabilizing process. A degree of hardness of the stationarycore 41 is relatively low and is substantially the same as the degree ofhardness of the movable core 40. The stationary core 41 is placed on anopposite side of the movable core 40, which is opposite from the valveseat 14. The stationary core 41 is placed in the inside of the housing20 such that an outer wall of the stationary core 41 is connected to aninner wall of the second tubular member 22 and an inner wall of thethird tubular member 23. An end surface of the stationary core 41, whichis located on the valve seat 14 side, is contactable with an end surfaceof the movable core 40, which is located on the stationary core 41 side.

An adjusting pipe 42, which is shaped into a cylindrical tubular form,is press fitted into the inside of the stationary core 41.

The spring 43 is, for example, a coil spring and is placed between theadjusting pipe 42, which is placed in the inside of the stationary core41, and the stepped surface 405 of the movable core 40. One end of thespring 43 contacts the adjusting pipe 42. The other end of the spring 43contacts the stepped surface 405. The spring 43 can urge the movablecore 40 together with the needle 30 toward the valve seat 14 side, i.e.,in the valve closing direction. An urging force of the spring 43 isadjusted by adjusting a position of the adjusting pipe 42 relative tothe stationary core 41.

The coil 44 is shaped into a generally cylindrical tubular form andsurrounds a radially outer side of the housing 20, particularly aradially outer side of the second tubular member 22 and a radially outerside of the third tubular member 23. Furthermore, a holder 45, which isshaped into a tubular form, is placed on a radially outer side of thecoil 44 such that the holder 45 covers the coil 44. The holder 45 ismade of a magnetic material, such as ferritic stainless steel. An innerwall of one end of the holder 45 is connected to an outer wall of thenozzle holder 26, and an inner wall of the other end of the holder 45 isconnected to an outer wall of the third tubular member 23.

When an electric power is supplied to the coil 44 (when the coil 44 isenergized), the coil 44 generates a magnetic force. When the magneticforce is generated at the coil 44, a magnetic circuit is formed throughthe stationary core 41, the movable core 40, the first tubular member21, the nozzle holder 26, the holder 45 and the third tubular member 23.In this way, a magnetic attractive force is generated between thestationary core 41 and the movable core 40, and thereby the movable core40 is magnetically attracted to the stationary core 41 together with theneedle 30. In this way, the needle 30 is moved in the valve openingdirection, and thereby the seat portion 31 is moved away from the valveseat 14 to result in valve opening. Thereby, the injection holes 13 areopened. As discussed above, when the coil 44 is energized, the movablecore 40 can be magnetically attracted toward the stationary core 41 tomove the needle 30 away from the valve seat 14 toward the opposite sidethat is opposite from the valve seat 14.

When the movable core 40 is magnetically attracted toward the stationarycore 41 (i.e., in the valve opening direction) by the magneticattractive force, the stationary core 41 side end surface of the movablecore 40 collides against the movable core 40 side end surface of thestationary core 41. In this way, movement of the movable core 40 in thevalve opening direction is limited.

When the energization of the coil 44 is stopped in the state where themovable core 40 is magnetically attracted to the stationary core 41, theneedle 30 and the movable core 40 are urged toward the valve seat 14 bythe urging force of the spring 43. In this way, the needle 30 is movedin the valve closing direction, and thereby the seat portion 31 contactsthe valve seat 14 to result in valve closing. Therefore, the injectionholes 13 are closed.

As shown in FIG. 1, a radially outer side of the third tubular member 23and a radially outer side of the coil 44 are resin molded by the moldingportion 46 that is made of resin. The connector portion 47 is formed toradially outwardly project from the molding portion 46. Terminals 471for supplying the electric power to the coil 44 are insert molded in theconnector portion 47. In a case where the housing 20 is divided into twoportions along an imaginary plane Vp1, which includes all of an axis Ax1of the nozzle tubular portion 11, the connector portion 47 is formed onone side of the imaginary plane Vp1 where one of the two portions isplaced. Furthermore, the fuel injection device 1 is installed to theengine 80 such that piston 82 is located on the one side of theimaginary plane Vp1, and the spark plug 97 is located on the other sideof the imaginary plane Vp1.

The fuel, which enters the inlet portion 24, flows through the filter25, the inside of the stationary core 41, the inside of the adjustingpipe 42, the spring 43, the inside of the movable core 40, the radialholes 403, the gap between the needle 30 and the inner wall of thehousing 20, and the gap between the needle 30 and the inner wall of thenozzle tubular portion 11, i.e., the fuel passage 100 and is guided tothe injection holes 13. At the time of operating the fuel injectiondevice 1, a surrounding space, which surrounds the movable core 40 andthe needle 30, is filled with the fuel. Furthermore, at the time ofoperating the fuel injection device 1, the fuel flows through the radialholes 403 of the movable core 40. Therefore, the movable core 40 and theneedle 30 can be smoothly reciprocated in the axial direction at theinside of the housing 20.

Next, the injection holes 13 of the present embodiment will be describedin detail with reference to FIGS. 3 and 4.

As shown in FIG. 3, each of the injection holes 13 includes an inletopening 131, an outlet opening 132 and an injection hole inner wall 133.The inlet opening 131 is formed at the surface 121 of the nozzle bottomportion 12, which is located on the side where the nozzle tubularportion 11 is placed. The outlet opening 132 is formed at the oppositesurface 122 of the nozzle bottom portion 12, which is opposite from thenozzle tubular portion 11.

A planar section 123 and a tapered section 124 are formed at the surface121. The planar section 123 is formed in a form of a planar circularsurface at a center of the surface 121. The axis Ax1 of the nozzletubular portion 11 extends through a center of the planar section 123,and the planar section 123 is substantially perpendicular to the axisAx1. The tapered section 124 is in a form of a ring and is formedcontinuously from the planar section 123 on a radially outer side of theplanar section 123. The tapered section 124 is tapered such that thetapered section 124 is progressively spaced away from the axis Ax1 ofthe nozzle tubular portion 11 from the planar section 123 toward thenozzle tubular portion 11. In the present embodiment, each inlet opening131 is formed at the tapered section 124.

The injection hole inner wall 133 is connected to the inlet opening 131and the outlet opening 132. Furthermore, the injection hole inner wall133 is tapered such that the injection hole inner wall 133 isprogressively spaced away from a central axis Ac of the injection hole13 from the inlet opening 131 side toward the outlet opening 132 side.

In the present embodiment, as shown in FIG. 4, the number of the inletopenings 131 of the injection holes 13 is six, and these inlet openings131 of the injection holes 13 are arranged one after another at equalintervals in the circumferential direction of the nozzle bottom portion12. Specifically, the inlet openings 131 of the six injection holes 13are arranged one after another at 60 degree intervals in thecircumferential direction of the nozzle bottom portion 12. Here, for thedescriptive purpose, the six injection holes 13 will be referred to asinjection holes 51, 52, 53, 54, 55, 56.

In the present embodiment, the injection holes 51, 52, 53, 54, 55, 56are arranged one after another in this order in the circumferentialdirection of the nozzle bottom portion 12 (see FIG. 4). The injectionholes 51-56 are placed one after another along an imaginary circle thatis centered at the axis Ax1 of the nozzle tubular portion 11. In thepresent embodiment, the fuel injection device 1 is installed to theengine 80 such that the injection holes 51, 52, 56 are placed on thespark plug 97 side of the imaginary plane Vp1, and the injection holes53, 54, 55 are placed on the piston 82 side of the imaginary plane Vp1.

Furthermore, since the inlet opening 131 and the outlet opening 132 ofeach injection hole 13 are formed at the tapered section 124 or a curvedsection of the nozzle bottom portion 12, the inlet opening 131 and theoutlet opening 132 respectively look like in a form of an ellipse inreality in a view taken in the axis Ax1. However, for the sake ofsimplicity, the inlet opening 131 and the outlet opening 132 arerespectively shaped in a form of a circle in FIG. 4.

Here, the injection holes 51, 52, 56 correspond to primary injectionholes of the claims. Furthermore, the injection holes 54, 53, 55correspond to secondary injection holes of the claims.

Furthermore, a set of the injection hole 51 and the injection hole 54, aset of the injection hole 52 and the injection hole 53 and a set of theinjection hole 56 and the injection hole 55 correspond to injection holesets of the claims. Specifically, in the present embodiment, theinjection holes 13 include three sets of injection holes.

Next, the injection hole set of the injection hole 51 and the injectionhole 54 will be described with reference to FIGS. 3 and 4.

The inlet opening 131, the outlet opening 132, the injection hole innerwall 133 and the central axis Ac of the injection hole 51, which servesas the primary injection hole, correspond to a primary inlet opening, aprimary outlet opening, a primary injection hole inner wall and aprimary central axis of the claims.

The inlet opening 131, the outlet opening 132, the injection hole innerwall 133 and the central axis Ac of the injection hole 54, which servesas the secondary injection hole, correspond to a secondary inletopening, a secondary outlet opening, a secondary injection hole innerwall and a secondary central axis of the claims.

In the present embodiment, as shown in FIG. 3, with respect to one ofthe injection hole sets (e.g., a first injection hole set: the injectionhole set of the injection hole 51 and the injection hole 54), γ (deg) isdefined as an injection-hole-to-injection-hole angle, which is an angleformed between the central axis (serving as the primary central axis)Ac11 of the injection hole 51 and the central axis (serving as thesecondary central axis) Ac12 of the injection hole 54; θt1 (deg) isdefined as a primary taper angle, which is an angle formed betweenoutlines of the injection hole inner wall (serving as the primaryinjection hole inner wall) 133 of the injection hole 51 in a crosssection of the injection hole inner wall 133 taken along an imaginaryplane that includes all of the primary central axis Ac11; θt2 (deg) isdefined as a secondary taper angle, which is an angle formed betweenoutlines of the injection hole inner wall (serving as the secondaryinjection hole inner wall) 133 of the injection hole 54 in a crosssection of the injection hole inner wall 133 taken along an imaginaryplane that includes all of the secondary central axis Ac12; and P (MPa)is defined as an average pressure of the fuel in the fuel passage 100 ata time of injecting the fuel from the plurality of injection holes 13.Under the above setting, the injection hole (serving as the primaryinjection hole) 51 and the injection hole (serving as the secondaryinjection hole) 54 are formed to satisfy a relationship of the followingequation 1.γ≤θt1+θt2−0.87×P{circumflex over ( )}0.52  Equation 1Here, {circumflex over ( )} of the equation 1 denotes “to a power of.”

Furthermore, in the present embodiment, the primary injection hole andthe secondary injection hole are formed to satisfy a relationship of thefollowing equation 2.θt1+θt2−10≤γ  Equation 2

Similarly, the primary injection hole and the secondary injection holeof the other injection hole sets (the injection hole set of theinjection hole 52 and the injection hole 53, and the injection hole setof the injection hole 56 and the injection hole 55) are also formed tosatisfy the relationships of the equation 1 and the equation 2 discussedabove. In the injection hole set of the injection hole 52 and theinjection hole 53, and the injection hole set of the injection hole 56and the injection hole 55, the primary central axis and the secondarycentral axis are skew to each other. In this case, theinjection-hole-to-injection-hole angle γ corresponds to an angle formedbetween the primary central axis and a straight line while the straightline extends from a point along the primary central axis in parallelwith the secondary central axis.

Furthermore, according to the above equation 1, there is satisfied thefollowing relationship.γ−(θt1+θt2)≤−0.87×P{circumflex over ( )}0.52

A pressure of the fuel in the fuel passage 100, which is assumed to beexerted in the fuel passage 100 during the use of the fuel injectiondevice 1 of the present embodiment, is, for example, about 20 MPa.Therefore, in the present embodiment, P is 20 (MPa), and−0.87×P{circumflex over ( )}0.52 is about −4 (deg).

Furthermore, in the present embodiment, the taper angle (θt1, θt2) ofeach of the injection holes 51-56 is set to be, for example, about 18(deg). Therefore, according to the equation 1 and the equation 2, thereis satisfied the following relationship.26≤γ≤32(deg)Furthermore, there is also satisfied the following relationship.γ−(θt1+θt2)/2≤14(deg)

As shown in FIG. 4, the fuel mist, which is injected from each of theinjection holes 51-56, is injected in a direction of a correspondingarrow that extends along the central axis Ac of the injection hole51-56.

With reference to FIG. 5, α (deg) is defined as a hole-set-to-hole-setangle that is an angle formed between: the primary central axis Ac11 orthe secondary central axis Ac12 of the first injection hole set (e.g.,the injection hole set of the injection hole 51 and the injection hole54), which is the one injection hole set selected from the threeinjection hole sets; and the primary central axis Ac21 or the secondarycentral axis Ac22 of the second injection hole set (e.g., the injectionhole set of the injection hole 52 and the injection hole 53), which isthe different injection hole set that is different from the firstinjection hole set among the three injection hole sets. Under the abovesetting, the first injection hole set and the second injection hole setare formed to satisfy a relationship of the following equation 3.γ<α  Equation 3This is also true with respect to the relationship relative to the otherinjection hole set (the injection hole set of the injection hole 56 andthe injection hole 55).

With reference to FIG. 6, C is defined as a circle, which is formed by aline of intersection between: a specific imaginary plane SVp (see FIG.3) that is an imaginary plane spaced from the nozzle bottom portion 12by a predetermined distance Dt on the opposite side, which is oppositefrom the nozzle tubular portion 11, while the imaginary plane isperpendicular to the axis Ax1 of the nozzle tubular portion 11; and animaginary conical surface that includes all of the primary injectionhole inner wall 133 of each injection hole 13. Then, C11 is defined as acircle that is formed by a line of intersection between: the specificimaginary plane SVp; and an imaginary conical surface that includes allof the primary injection hole inner wall of the first injection hole set(e.g., the injection hole set of the injection hole 51 and the injectionhole 54). C12 is defined as a circle that is formed by a line ofintersection between: the specific imaginary plane SVp; and an imaginaryconical surface that includes all of the secondary injection hole innerwall of the first injection hole set. C21 is defined as a circle that isformed by a line of intersection between: the specific imaginary planeSVp; and an imaginary conical surface that includes all of the primaryinjection hole inner wall of the second injection hole set (e.g., theinjection hole set of the injection hole 52 and the injection hole 53).C22 is defined as a circle that is formed by a line of intersectionbetween: the specific imaginary plane SVp; and an imaginary conicalsurface that includes all of the secondary injection hole inner wall ofthe second injection hole set. Furthermore, d1 is defined as a distancebetween C11 and C12. Also, d2 is defined as a distance between: C11 orC12; and C21 or C22. Under the above setting, the first injection holeset and the second injection hole set are formed to satisfy arelationship of the following equation 4.d1<d2  Equation 4This is also true with respect to the relationship relative to the otherinjection hole set (the injection hole set of the injection hole 56 andthe injection hole 55).

In the present embodiment, each injection hole 13 is formed such thatthe circle C, which is formed by the line of intersection between thespecific imaginary plane SVp and the imaginary conical surface includingall of the injection hole inner wall 133 of the injection hole 13, isplaced on the piston 82 side of the imaginary plane Vp1.

In FIG. 6, each line of intersection (Cf1-Cf6) between the outline ofthe fuel mist injected from the corresponding injection hole 51-56 andthe specific imaginary plane SVp is indicated by a dot-dot-dash line. Inthe present embodiment, the injection holes 51-56 satisfy therelationships of the equation 1 and the equation 2, and each injectionhole set satisfies the relationships of the equation 3 and the equation4. Therefore, the Coanda effect can be generated between the fuel mist,which is injected from the injection hole 51, and the fuel mist, whichis injected from the injection hole 54. Also, the Coanda effect can begenerated between the fuel mist, which is injected from the injectionhole 52, and the fuel mist, which is injected from the injection hole53. Additionally, the Coanda effect can be generated between the fuelmist, which is injected from the injection hole 56, and the fuel mist,which is injected from the injection hole 55. In the present embodiment,a center of Cf1 is generally placed on C11, and a center of Cf4 isgenerally placed on C12. Also, a center of Cf2 is generally placed onC21, and a center of Cf3 is generally placed on C22.

Since FIGS. 3 to 6 are schematic diagrams, FIGS. 3 to 6 do notaccurately indicate the taper angle, theinjection-hole-to-injection-hole angle, the hole-set-to-hole-set angleand the distances for the respective injection holes. Furthermore, theprimary central axis and the secondary central axis obliquely intersectwith the specific imaginary plane SVp, so that the C11, C12, C21, C22,Cf1-Cf6 respectively look like in a form of an ellipse in reality in aview taken in the axial direction of the axis Ax1. However, for the sakeof simplicity, C11, C12, C21, C22, Cf1-Cf6 are respectively shaped in aform of a circle in FIGS. 4 and 6.

Next, FIG. 7 indicates a relationship between γ−(θt1+θt2) and the degreeof influence of the Coanda effect in the case where the pressure of thefuel in the fuel passage 100 is about 20 MPa that is assumed to beexerted in the fuel passage during the use of the fuel injection device1 of the present embodiment. The result of the experiment, in which thefuel is injected from the fuel injection device 1, is indicated byplotting a plurality of circles in FIG. 7.

In general, when the pressure of the fuel to be injected (the pressureof the fuel in the fuel passage 100) is increased, the mist angle isincreased, and thereby the degree of influence of the Coanda effect isincreased. In a case where the pressure of the fuel in the fuel passage100 is, for example, about 4 MPa, the influence of the Coanda effect canbe substantially ignored. Therefore, the degree of influence of theCoanda effect (hereinafter, also referred to as “Coanda influencedegree”) is defined by a ratio between “an angle θ_(20 MPa) of the fuelmist Fo, which is pulled in the case where P is 20”, and “an angleθ_(4 MPa) of the fuel mist Fo, which is pulled in the case where P is4”, and the degree of influence of the Coanda effect is indicated at anaxis of ordinates in FIG. 7.

As shown in FIG. 7, in a case where γ−(θt1+θt2) is −10.0 to −4.0, theCoanda influence degree is about 1.0 to 1.1. Therefore, in this range,the degree of influence of the Coanda effect can be stabilized, andthereby the Coanda effect can be stably generated between the fuel mist,which is injected from the primary injection hole, and the fuel mist,which is injected from the secondary injection hole.

In contrast, in the case where γ−(θt1+θt2) is equal to or smaller than−10.0 or is equal to or larger than −4.0, the Coanda influence degree isabout 0.8 to 1.4. Therefore, it is understood that the degree ofinfluence of the Coanda effect becomes unstable in this range, andthereby it is difficult to stably generate the Coanda effect between thefuel mist, which is injected from the primary injection hole, and thefuel mist, which is injected from the secondary injection hole.

In the case where γ−(θt1+θt2) is equal to or smaller than −10.0, thefuel mists may possibly collide with each other to cause an increase ina mist particle size of the fuel mists.

In the present embodiment, the injection holes 51-56 are formed toparticularly satisfy the relationships of the equation 1 and theequation 2 described above. Therefore, the collision between the fuelmists can be limited while the Coanda effect is effectively generatedbetween the fuel mists at the injection hole set.

As discussed above, (1) the fuel injection device 1 of the presentembodiment includes the nozzle 10.

The nozzle 10 includes: the nozzle tubular portion 11 that forms thefuel passage 100 in the inside of the nozzle tubular portion 11; thenozzle bottom portion 12 that closes the one end of the nozzle tubularportion 11; and the plurality of injection holes 13 that connect betweenthe surface 121 of the nozzle bottom portion 12, which is located on theside where the nozzle tubular portion 11 is placed, and the oppositesurface 122 of the nozzle bottom portion 12, which is located on theopposite side that is opposite from the nozzle tubular portion 11, toinject the fuel of the fuel passage 100.

The injection holes 13 include at least one injection hole set (the setof the injection hole 51 and the injection hole 54, the set of theinjection hole 52 and the injection hole 53, the set of the injectionhole 56 and the injection hole 55) that includes the primary injectionhole (the injection hole 51, the injection hole 52 or the injection hole56) and the secondary injection hole (the injection hole 54, theinjection hole 53 or the injection hole 55).

Each of the injection holes 51, 52, 56, which respectively serve as theprimary injection hole, includes: the inlet opening (serving as theprimary inlet opening) 131, which is formed at the nozzle tubularportion 11 side surface 121 of the nozzle bottom portion 12; the outletopening (serving as the primary outlet opening) 132, which is formed atthe opposite surface 122 of the nozzle bottom portion 12 located on theopposite side that is opposite from the nozzle tubular portion 11; andthe injection hole inner wall (serving as the primary injection holeinner wall) 133, which connects between the inlet opening 131 and theoutlet opening 132 and is tapered such that the injection hole innerwall 133 is progressively spaced away from the central axis (serving asthe primary central axis) Ac1 from the inlet opening 131 side toward theoutlet opening 132 side.

Each of the injection holes 54, 53, 55, which respectively serve as thesecondary injection hole, includes: the inlet opening (serving as thesecondary inlet opening) 131, which is formed at the surface 121 of thenozzle bottom portion 12 located on the side where the nozzle tubularportion 11 is placed; the outlet opening (serving as the secondaryoutlet opening) 132, which is formed at the opposite surface 122 of thenozzle bottom portion 12 located on the opposite side that is oppositefrom the nozzle tubular portion 11; and the injection hole inner wall(serving as the secondary injection hole inner wall) 133, which connectsbetween the inlet opening 131 and the outlet opening 132 and is taperedsuch that the injection hole inner wall 133 is progressively spaced awayfrom the central axis (serving as the secondary central axis) Ac1 fromthe inlet opening 131 side toward the outlet opening 132.

According to the present embodiment, with respect to one of theinjection hole sets (the first injection hole set: the injection holeset of the injection hole 51 and the injection hole 54), γ (deg) isdefined as the injection-hole-to-injection-hole angle, which is theangle formed between the central axis (serving as the primary centralaxis) Ac11 of the injection hole 51 and the central axis (serving as thesecondary central axis) Ac12 of the injection hole 54; θt1 (deg) isdefined as the primary taper angle, which is the angle formed betweenthe outlines of the injection hole inner wall (serving as the primaryinjection hole inner wall) 133 of the injection hole 51 in the crosssection of the injection hole inner wall 133 taken along the imaginaryplane that includes all of the primary central axis Ac11; θt2 (deg) isdefined as the secondary taper angle, which is the angle formed betweenthe outlines of the injection hole inner wall (serving as the secondaryinjection hole inner wall) 133 of the injection hole 54 in the crosssection of the injection hole inner wall 133 taken along the imaginaryplane that includes all of the secondary central axis Ac12; and P (MPa)is defined as the average pressure of the fuel in the fuel passage 100at the time of injecting the fuel from the plurality of injection holes13. Under the above setting, the injection hole (serving as the primaryinjection hole) 51 and the injection hole (serving as the secondaryinjection hole) 54 are formed to satisfy the relationship of thefollowing equation 1.γ≤θt1+θt2−0.87×P{circumflex over ( )}0.52  Equation 1

In the present embodiment, the primary injection hole and the secondaryinjection hole are formed to satisfy the equation 1, so that the Coandaeffect can be effectively generated between the fuel mist, which isinjected from the primary injection hole, and the fuel mist, which isinjected from the secondary injection hole.

Furthermore, according to the present embodiment, the primary injectionhole inner wall and the secondary injection hole inner wall are tapered,so that the primary injection hole or the secondary injection holedischarges the fuel to spread the fuel. Therefore, it is possible toreduce a difference between: the mist angle of the fuel mist, which isinjected from each injection hole 13 in the state where the fuelpressure in the fuel passage 100 is high; and the mist angle of the fuelmist, which is injected from each injection hole 13 in the state wherethe fuel pressure in the fuel passage 100 is low. Therefore, even whenthe fuel pressure in the fuel passage 100 changes, it is possible tolimit a change in the mist angle of the fuel mist, which is injectedfrom the primary injection hole or the secondary injection hole.Thereby, regardless of the change in the fuel pressure, the Coandaeffect can be stably generated between the fuel mist, which is injectedfrom the primary injection hole, and the fuel mist, which is injectedfrom the secondary injection hole. Thus, regardless of the change in thefuel pressure, a rich mixture gas, which is atomized at the area betweenthe fuel mists, can be stably generated.

Furthermore, (2) according to the present embodiment, the primaryinjection hole and the secondary injection hole are formed to satisfythe relationship of the following equation 2.θt1+θt2−10≤γ  Equation 2Therefore, it is possible to limit occurrence of collision between thefuel mists that would cause interference against the atomization of thefuel mist at the center side between the fuel mists.

Furthermore, (3), according to the present embodiment, the injectionholes 13 include the three injection hole sets.

Here, α (deg) is defined as the hole-set-to-hole-set angle that is theangle formed between: the primary central axis or the secondary centralaxis of the first injection hole set, which is the one injection holeset selected from the three injection hole sets; and the primary centralaxis or the secondary central axis of the second injection hole set,which is the different injection hole set that is different from thefirst injection hole set among the three injection hole sets. Under theabove setting, the first injection hole set and the second injectionhole set are formed to satisfy the relationship of the followingequation 3.γ<α  Equation 3Therefore, the Coanda effect may be effectively generated between thefuel mists that are injected from the one injection hole set whilegeneration of the Coanda effect may be minimized between: any one of thefuel mists that are injected from the one injection hole set; and anyone of the fuel mists that are injected from the other injection holeset. Therefore, in the structure that includes the plurality ofinjection hole sets, regardless of the change in the fuel pressure, therich mixture gas, which is atomized at the center side between the fuelmists, can be more stably generated.

Furthermore, (4) according to the present embodiment, C11 is defined asthe circle that is formed by the line of intersection between: thespecific imaginary plane SVp; and the imaginary conical surface thatincludes all of the primary injection hole inner wall of the firstinjection hole set. The specific imaginary plane SVp is the imaginaryplane spaced from the nozzle bottom portion 12 by the predetermineddistance Dt on the opposite side, which is opposite from the nozzletubular portion 11, while the imaginary plane is perpendicular to theaxis Ax1 of the nozzle tubular portion 11. C12 is defined as the circlethat is formed by the line of intersection between: the specificimaginary plane SVp; and the imaginary conical surface that includes allof the secondary injection hole inner wall of the first injection holeset. C21 is defined as the circle that is formed by the line ofintersection between: the specific imaginary plane SVp; and theimaginary conical surface that includes all of the primary injectionhole inner wall of the second injection hole set. C22 is defined as thecircle that is formed by the line of intersection between: the specificimaginary plane SVp; and the imaginary conical surface that includes allof the secondary injection hole inner wall of the second injection holeset. Furthermore, d1 is defined as the distance between C11 and C12.Also, d2 is defined as the distance between: C11 or C12; and C21 or C22.Under the above setting, the first injection hole set and the secondinjection hole set are formed to satisfy a relationship of the followingequation 4.d1<d2  Equation 4Therefore, the Coanda effect may be effectively generated between thefuel mists that are injected from the one injection hole set whilegeneration of the Coanda effect may be minimized between: any one of thefuel mists that are injected from the one injection hole set; and anyone of the fuel mists that are injected from the other injection holeset. Thereby, in the structure that includes the plurality of injectionhole sets, regardless of the change in the fuel pressure, the richmixture gas, which is atomized at the center side between the fuelmists, can be further stably generated.

Furthermore, (5) according to the present embodiment, the nozzle 10includes the valve seat 14 that is formed at the inner wall of thenozzle 10. The fuel injection device 1 of the present embodiment furtherincludes the housing 20, the needle 30, the movable core 40, thestationary core 41, the coil 44 and the spring 43.

The housing 20 is shaped into the tubular form and is connected to theopposite side of the nozzle tubular portion 11, which is opposite fromthe nozzle bottom portion 12.

The needle 30 is placed in the inside of the housing 20 such that theneedle 30 has the one end, which is contactable with the valve seat 14,and the needle 30 is operable to reciprocate in the axial direction.When the one end of the needle 30 is lifted from the valve seat 14 orcontacts the valve seat 14, the needle 30 opens or closes the injectionholes 13.

The movable core 40 is placed such that the movable core 40 is operableto reciprocate in the inside of the housing 20 together with the needle30.

The stationary core 41 is placed on the opposite side of the movablecore 40, which is opposite from the valve seat 14, in the inside of thehousing 20.

The coil 44 is operable to attract the movable core 40 toward thestationary core 41 to move the needle 30 toward the opposite side thatis opposite from the valve seat 14 at the time of energizing the coil44.

The spring 43 is operable to urge the needle 30 and the movable core 40toward the valve seat 14.

As discussed above, the fuel injection device 1 of the presentembodiment is a fuel injection device of an electromagnetic drive type.

Second Embodiment

FIG. 8 indicates a portion of a fuel injection device according to asecond embodiment of the present disclosure.

In the second embodiment, the injection hole 51 is formed such that thecircle C, which is formed by the line of intersection between: thespecific imaginary plane SVp; and the imaginary conical surface thatincludes all of the injection hole inner wall 133 of the injection hole51, is located on the spark plug 97 side of the imaginary plane Vp1.

Each of the injection holes 53, 54, 55 is formed such that the circle C,which is formed by the line of intersection between: the specificimaginary plane SVp; and the imaginary conical surface that includes allof the injection hole inner wall 133 of the injection hole 53, 54, 55,is located on the piston 82 side of the imaginary plane Vp1.

The rest of the structure of the second embodiment, which is other thanthe above-described points, is the same as that of the first embodiment.

Even in the second embodiment, advantages, which are similar to those ofthe first embodiment, can be achieved.

Third Embodiment

FIG. 9 indicates a portion of a fuel injection device according to athird embodiment of the present disclosure.

In the third embodiment, α (deg) is defined as a hole-set-to-hole-setangle that is an angle formed between: the primary central axis Ac11 orthe secondary central axis Ac12 of the first injection hole set (e.g.,the injection hole set of the injection hole 51 and the injection hole54), which is the one injection hole set selected from the threeinjection hole sets; and the primary central axis Ac21 or the secondarycentral axis Ac22 of the second injection hole set (e.g., the injectionhole set of the injection hole 52 and the injection hole 53), which isthe different injection hole set that is different from the firstinjection hole set among the three injection hole sets. Under the abovesetting, the first injection hole set and the second injection hole setare formed to satisfy the relationship of the following equation 3.γ<α  Equation 3

However, in the present embodiment, C11 is defined as the circle that isformed by the line of intersection between: the specific imaginary planeSVp; and the imaginary conical surface that includes all of the primaryinjection hole inner wall of the first injection hole set (e.g., theinjection hole set of the injection hole 51 and the injection hole 54).C12 is defined as the circle that is formed by the line of intersectionbetween: the specific imaginary plane SVp; and the imaginary conicalsurface that includes all of the secondary injection hole inner wall ofthe first injection hole set. C21 is defined as the circle that isformed by the line of intersection between: the specific imaginaryplane; and the imaginary conical surface that includes all of theprimary injection hole inner wall of the second injection hole set(e.g., the injection hole set of the injection hole 52 and the injectionhole 53). C22 is defined as the circle that is formed by the line ofintersection between: the specific imaginary plane SVp; and theimaginary conical surface that includes all of the secondary injectionhole inner wall of the second injection hole set. Furthermore, d1 isdefined as the distance between C11 and C12. Also, d2 is defined as thedistance between: C11 or C12; and C21 or C22. Under the above setting,the first injection hole set and the second injection hole set areformed to satisfy a relationship of the following equation 5.d1>d2  Equation 5

This is also true with respect to the relationship relative to the otherinjection hole set (the injection hole set of the injection hole 56 andthe injection hole 55).

As described above, according to the present embodiment, unlike thefirst embodiment, the first injection hole set and the second injectionhole set are formed to satisfy the above equation 5 rather than theabove equation 4. However, in the present embodiment, similar to thefirst embodiment, the first injection hole set and the second injectionhole set are formed to satisfy the above equation 3. Therefore, even inthe third embodiment, advantages, which are similar to those of thefirst embodiment, can be achieved.

Fourth Embodiment

FIGS. 10 and 11 show a fuel injection device according to a fourthembodiment of the present disclosure. The fourth embodiment differs fromthe first embodiment with respect to an installation location of thefuel injection device 1 and the like at the engine 80.

As shown in FIG. 10, in the present embodiment, the fuel injectiondevice 1 is placed at a corresponding location of the cylinder head 90,which is between the intake valve 95 and the exhaust valve 96, i.e., acorresponding location of the cylinder head 90 that corresponds to acenter of the combustion chamber 83. The fuel injection device 1 isplaced such that an axis of the fuel injection device 1 is generallyparallel to the axis of the combustion chamber 83 or substantiallycoincides with the axis of the combustion chamber 83. In the presentembodiment, the fuel injection device 1 is placed in the center at theupper side of the engine 80 in the vertical direction. That is, the fuelinjection device 1 is mounted to the center of the engine 80.

Furthermore, at the cylinder block 81 side of the exhaust manifold 93,the spark plug 97 is placed at the location where the fuel injected fromthe fuel injection device 1 does not directly adhere to the spark plug97, and the spark plug 97 can ignite the mixture gas (combustible air),which is the mixture of the fuel and the intake air.

The fuel injection device 1 is installed to the engine 80 such that theintake valve 95 is placed on one side of the imaginary plane Vp1, andthe exhaust valve 96 and the spark plug 97 are placed on the other sideof the imaginary plane Vp1.

The fuel injection device 1 is placed such that the injection holes 13are exposed to an opposite side of the combustion chamber 83 that isopposite from the piston 82 in the axial direction. The conical fuelmist Fo is injected from the respective injection holes 13 of the fuelinjection device 1 into the combustion chamber 83.

As shown in FIG. 11, in the fourth embodiment, the fuel injection device1 is installed to the engine 80 such that the injection holes 51, 56 areplaced on the exhaust valve 96 side of the imaginary plane Vp1, and theinjection holes 52, 55 are slightly deviated relative to the imaginaryplane Vp1 toward the intake valve 95 side, and the injection holes 53,54 are placed on the intake valve 95 side of the imaginary plane Vp1.

In the fourth embodiment, the injection holes 13 include three injectionhole sets (an injection hole set of the injection hole 51 and theinjection hole 52, an injection hole set of the injection hole 53 andthe injection hole 54, and an injection hole set of the injection hole55 and the injection hole 56).

According to the present embodiment, with respect to one of theinjection hole sets (e.g., the first injection hole set: the injectionhole set of the injection hole 51 and the injection hole 52), γ (deg) isdefined as the injection-hole-to-injection-hole angle, which is theangle formed between the central axis (serving as the primary centralaxis) Ac11 of the injection hole 51 and the central axis (serving as thesecondary central axis) Ac12 of the injection hole 52; θt1 (deg) isdefined as the primary taper angle, which is the angle formed betweenthe outlines of the injection hole inner wall (serving as the as theprimary injection hole inner wall) 133 of the injection hole 51 in thecross section of the injection hole inner wall 133 taken along theimaginary plane that includes all of the primary central axis Ac11; θt2(deg) is defined as the secondary taper angle, which is the angle formedbetween the outlines of the injection hole inner wall (serving as thesecondary injection hole inner wall) 133 of the injection hole 52 in thecross section of the injection hole inner wall 133 taken along theimaginary plane that includes all of the secondary central axis Ac12;and P (MPa) is defined as the average pressure of the fuel in the fuelpassage 100 at the time of injecting the fuel from the plurality ofinjection holes 13. Under the above setting, the injection hole (servingas the primary injection hole) 51 and the injection hole (serving as thesecondary injection hole) 52 are formed to satisfy the relationship ofthe following equation 1.γ≤θt1+θt2−0.87×P{circumflex over ( )}0.52  Equation 1

Furthermore, according to the present embodiment, the primary injectionhole and the secondary injection hole are formed to satisfy therelationship of the following equation 2θt1+θt2−10≤γ  Equation 2

Similarly, the primary injection hole and the secondary injection holeof the other injection hole sets (the injection hole set of theinjection hole 53 and the injection hole 54, and the injection hole setof the injection hole 55 and the injection hole 56) are also formed tosatisfy the relationships of the equation 1 and the equation 2.

Furthermore, α (deg) is defined as the hole-set-to-hole-set angle thatis the angle formed between: the primary central axis Ac11 or thesecondary central axis Ac12 of the first injection hole set (e.g., theinjection hole set of the injection hole 51 and the injection hole 52),which is the one injection hole set selected from the three injectionhole sets; and the primary central axis Ac21 or the secondary centralaxis Ac22 of the second injection hole set (e.g., the injection hole setof the injection hole 53 and the injection hole 54), which is thedifferent injection hole set that is different from the first injectionhole set among the three injection hole sets. Under the above setting,the first injection hole set and the second injection hole set areformed to satisfy the relationship of the following equation 3.γ<α  Equation 3

Furthermore, in the present embodiment, C11 is defined as the circlethat is formed by the line of intersection between: the specificimaginary plane SVp; and the imaginary conical surface that includes allof the primary injection hole inner wall of the first injection hole set(e.g., the injection hole set of the injection hole 51 and the injectionhole 52). C12 is defined as the circle that is formed by the line ofintersection between: the specific imaginary plane SVp; and theimaginary conical surface that includes all of the secondary injectionhole inner wall of the first injection hole set. C21 is defined as thecircle that is formed by the line of intersection between: the specificimaginary plane; and the imaginary conical surface that includes all ofthe primary injection hole inner wall of the second injection hole set(e.g., the injection hole set of the injection hole 53 and the injectionhole 54). C22 is defined as the circle that is formed by the line ofintersection between: the specific imaginary plane SVp; and theimaginary conical surface that includes all of the secondary injectionhole inner wall of the second injection hole set. Furthermore, d1 isdefined as the distance between C11 and C12. Also, d2 is defined as thedistance between: C11 or C12; and C21 or C22. Under the above setting,the first injection hole set and the second injection hole set areformed to satisfy the relationship of the following equation 5.d1>d2  Equation 5

This is also true with respect to the relationship relative to the otherinjection hole set (the injection hole set of the injection hole 55 andthe injection hole 56).

Even in the fourth embodiment, advantages, which are similar to those ofthe first embodiment, can be achieved.

Fifth Embodiment

FIG. 12 indicates a portion of a fuel injection device according to afifth embodiment of the present disclosure. The fifth embodiment differsfrom the fourth embodiment with respect to a way of installing the fuelinjection device 1 at the engine 80.

In the fifth embodiment, the fuel injection device 1 is installed to theengine 80 such that the injection holes 51, 52, 56 are placed on theexhaust valve 96 side of the imaginary plane Vp1, and the injectionholes 53, 54, 55 are placed on the intake valve 95 side of the imaginaryplane Vp1.

In the fifth embodiment, the injection holes 13 include the threeinjection hole sets (the injection hole set of the injection hole 51 andthe injection hole 52, the injection hole set of the injection hole 53and the injection hole 54, and the injection hole set of the injectionhole 55 and the injection hole 56).

In the present embodiment, similar to the fourth embodiment, theinjection holes 51-56 are formed to satisfy the equation 1 and theequation 2 described above. Furthermore, the three injection hole setsare formed to satisfy the relationship of the above equation 3.

In the present embodiment, the distance between the outlet opening 132of the injection hole 51 and the axis Ax1 is set to be larger than thedistance between the outlet opening 132 of each of the injection holes52-56 and the axis Ax1.

Even in the fifth embodiment, advantages, which are similar to those ofthe fourth embodiment, can be achieved.

Sixth Embodiment

FIG. 13 indicates a portion of a fuel injection device according to asixth embodiment of the present disclosure. The sixth embodiment differsfrom the fifth embodiment with respect to a way of installing the fuelinjection device 1 at the engine 80. In the sixth embodiment, the fuelinjection device 1 is installed to the engine 80 such that the injectionholes 51, 55, 56 are placed on the exhaust valve 96 side of theimaginary plane Vp1, and the injection holes 52, 53, 54 are placed onthe intake valve 95 side of the imaginary plane Vp1.

In the sixth embodiment, the injection holes 13 include the threeinjection hole sets (the injection hole set of the injection hole 51 andthe injection hole 52, the injection hole set of the injection hole 53and the injection hole 54, and the injection hole set of the injectionhole 55 and the injection hole 56).

In the present embodiment, similar to the fifth embodiment, theinjection holes 51-56 are formed to satisfy the equation 1 and theequation 2 described above. Furthermore, the three injection hole setsare formed to satisfy the relationship of the above equation 3.

In the present embodiment, the distance between the outlet opening 132of each of the injection holes 51-56 and the axis Ax1 is set to beidentical.

Even in the sixth embodiment, advantages, which are similar to those ofthe fifth embodiment, can be achieved.

Other Embodiments

In another embodiment of the present disclosure, the primary injectionhole and the secondary injection hole may be formed to satisfy only theabove equation 1. That is, it is not required to form the primaryinjection hole and the secondary injection hole to satisfy the aboveequation 2. Furthermore, it is not required to form the first injectionhole set and the second injection hole set to satisfy the equation 3 andthe equation 4 described above. In the case where the primary injectionhole and the secondary injection hole are formed to satisfy the equation1 and the equation 2, and the first injection hole set and the secondinjection hole set are formed to satisfy the equation 3 and the equation4 like in the first embodiment, the various advantages discussed in thefirst embodiment can be achieved.

In the above embodiments, there are described the exemplary cases wherethe injection holes 13 include the three injection hole sets.Alternatively, in another embodiment of the present disclosure, theinjection holes 13 may include one injection hole set, two injectionhole sets, four injection hole sets or more.

In the above embodiments, the taper angle (θt1, θt2) of each of theinjection holes 51-56 is set to, for example, about 18 (deg).Alternatively, in another embodiment of the present disclosure, thetaper angle θt1, θt2 may be set to any value as long as the taper angleθt1, θt2 is larger than 0 degrees and is smaller than 90 degrees.

In the above embodiments, there are described the exemplary cases wherethe movable core 40 is formed integrally with the needle 30. Incontrast, according to another embodiment of the present disclosure, themovable core 40 may be formed to be movable relative to the needle 30,and the needle 30 may have a surface that is contactable with themovable core 40 and is placed on the valve seat 14 side. In this case,it is desirable to have a stationary core side urging member that urgesthe movable core 40 toward the stationary core 41 side.

Furthermore, in another embodiment of the present disclosure, the nozzletubular portion 11 of the nozzle 10 and the first tubular member 21 ofthe housing 20 may be integrally formed in one piece. Furthermore, thenozzle tubular portion 11 and the nozzle bottom portion 12 may beseparately formed.

In another embodiment of the present disclosure, the fuel injectiondevice may not have the valve seat 14, the housing 20, the needle 30,the movable core 40, the stationary core 41, the coil 44 and the spring43 and may only include the nozzle 10. In such a case, the fuelinjection device may be installed to a fuel supply portion, to which thefuel is intermittently or continuously supplied, so that the fuelinjection device injects the fuel from the injection holes 13.

In another embodiment of the present disclosure, the average pressure Pof the fuel passage 100 at the time of injecting the fuel from theinjection holes 13 is not necessary limited to 20 MPa and may be in arange of about 20 to 100 MPa.

Furthermore, in the above embodiments, there are described the exemplarycases where the fuel injection device is installed to the directinjection gasoline engine. Alternatively, in another embodiment of thepresent disclosure, the fuel injection device may be applied to a dieselengine or a port injection gasoline engine.

As described above, the present disclosure should not be limited to theabove embodiments and may be implemented in various other forms withoutdeparting from the scope of the present disclosure.

The invention claimed is:
 1. A fuel injection device comprising a nozzlethat includes: a nozzle tubular portion that forms a fuel passage in aninside of the nozzle tubular portion; a nozzle bottom portion thatcloses one end of the nozzle tubular portion; and a plurality ofinjection holes that connect between one surface of the nozzle bottomportion, which is located on a side where the nozzle tubular portion isplaced, and an opposite surface of the nozzle bottom portion, which islocated on an opposite side that is opposite from the nozzle tubularportion, to inject fuel of the fuel passage, wherein: the plurality offuel injection holes includes at least one injection hole set thatincludes: a primary injection hole that has: a primary inlet opening,which is formed at the one surface of the nozzle bottom portion locatedon the side where the nozzle tubular portion is placed; a primary outletopening, which is formed at the opposite surface of the nozzle bottomportion located on the opposite side that is opposite from the nozzletubular portion; and a primary injection hole inner wall, which istapered such that the primary injection hole inner wall is progressivelyspaced away from a primary central axis, which is a central axis of theprimary injection hole, from the primary inlet opening side toward theprimary outlet opening side; and a secondary injection hole that has: asecondary inlet opening, which is formed at the one surface of thenozzle bottom portion located on the side where the nozzle tubularportion is placed; a secondary outlet opening, which is formed at theopposite surface of the nozzle bottom portion located on the oppositeside that is opposite from the nozzle tubular portion; and a secondaryinjection hole inner wall, which is tapered such that the secondaryinjection hole inner wall is progressively spaced away from a secondarycentral axis, which is a central axis of the secondary injection hole,from the secondary inlet opening side toward the secondary outletopening side; with respect to the injection hole set, γ (deg) is definedas an injection-hole-to-injection-hole angle, which is an angle formedbetween the primary central axis and a straight line while the straightline extends from a point along the primary central axis in parallelwith the secondary central axis; θt1 (deg) is defined as a primary taperangle, which is an angle formed between outlines of the primaryinjection hole inner wall in a cross section of the primary injectionhole inner wall taken along an imaginary plane that includes all of theprimary central axis; θt2 (deg) is defined as a secondary taper angle,which is an angle formed between outlines of the secondary injectionhole inner wall in a cross section of the secondary injection hole innerwall taken along an imaginary plane that includes all of the secondarycentral axis; and P (MPa) is defined as an average pressure of the fuelin the fuel passage at a time of injecting the fuel from the pluralityof injection holes; and the primary injection hole and the secondaryinjection hole are formed to satisfy a relationship of the followingequation 1:0<γ≤θt1+θt2−0.87×P{circumflex over ( )}0.52  Equation 1 where{circumflex over ( )} of the equation 1 denotes “to a power of.”
 2. Thefuel injection device according to claim 1, wherein the primaryinjection hole and the secondary injection hole are adjacent to eachother in a circumferential direction of the nozzle bottom portion. 3.The fuel injection device according to claim 1, wherein the primaryinjection hole and the secondary injection hole are formed to satisfy arelationship of the following equation 2:θt1+θt2−10≤γ  Equation
 2. 4. The fuel injection device according toclaim 1, wherein: the at least one injection hole set of the pluralityof injection holes includes a plurality of injection hole sets; α (deg)is defined as a hole-set-to-hole-set angle that is an angle formedbetween: the primary central axis or the secondary central axis of afirst injection hole set, which is a selected one that is selected fromthe plurality of injection hole sets; and the primary central axis orthe secondary central axis of a second injection hole set, which is adifferent injection hole set that is different from the first injectionhole set among the plurality of injection hole sets; and the firstinjection hole set and the second injection hole set are formed tosatisfy a relationship of the following equation 3:γ<α  Equation
 3. 5. The fuel injection device according to claim 4,wherein: C11 is defined as a circle that is formed by a line ofintersection between: a specific imaginary plane that is an imaginaryplane spaced from the nozzle bottom portion by a predetermined distanceon the opposite side, which is opposite from the nozzle tubular portion,while the imaginary plane is perpendicular to an axis of the nozzletubular portion; and an imaginary conical surface that includes all ofthe primary injection hole inner wall of the first injection hole set;C12 is defined as a circle that is formed by a line of intersectionbetween: the specific imaginary plane; and an imaginary conical surfacethat includes all of the secondary injection hole inner wall of thefirst injection hole set; C21 is defined as a circle that is formed by aline of intersection between: the specific imaginary plane; and animaginary conical surface that includes all of the primary injectionhole inner wall of the second injection hole set; C22 is defined as acircle that is formed by a line of intersection between: the specificimaginary plane; and an imaginary conical surface that includes all ofthe secondary injection hole inner wall of the second injection holeset; d1 is defined as a distance between C11 and C12; d2 is defined as adistance between: C11 or C12; and C21 or C22; and the first injectionhole set and the second injection hole set are formed to satisfy arelationship of the following equation 4:d1<d2  Equation
 4. 6. The fuel injection device according to claim 1,wherein: the nozzle includes a valve seat that is formed at an innerwall of the nozzle; and the fuel injection device further comprising: ahousing that is shaped into a tubular form and is connected to anopposite side of the nozzle tubular portion, which is opposite from thenozzle bottom portion; a needle that is placed in an inside of thehousing such that the needle has one end, which is contactable with thevalve seat, and the needle is operable to reciprocate in an axialdirection, wherein when the one end of the needle is lifted from thevalve seat or contacts the valve seat, the needle opens or closes theplurality of injection holes; a movable core that is placed such thatthe movable core is operable to reciprocate in an inside of the housingtogether with the needle; a stationary core that is placed on anopposite side of the movable core, which is opposite from the valveseat, in the inside of the housing; a coil that is operable to attractthe movable core toward the stationary core to move the needle toward anopposite side that is opposite from the valve seat at a time ofenergizing the coil; and a valve seat side urging member that isoperable to urge the needle and the movable core toward the valve seat.